In response to security threats in transportation and public spaces, inspection of people for weapons and other types of contraband is becoming common at security checkpoints at, for example, airports, train stations, sporting events, concerts, federal buildings, and other public and private facilities. Systems using non-ionizing radiation, such as terahertz and millimeter wave, for imaging of concealed weapons, contraband or other items of interest are known. Such systems are described in, for example, U.S. Pat. Nos. 6,972,714, 6,965,340, 7,112,775, 7,224,314, 7,283,085, 7,333,055, 7,327,304, 7,280,068, 7,298,318, and 7,525,500 and U.S. Patent Appl. Pub. Nos. 2005-0270220, 2006-0109160, 2006-0214836, 2008-0161685, 2008-0094301, 2008-0094296.
Other prior publications in this field include US20080043102, WO200678570, U.S. Pat. No. 7,119,731, U.S. Pat. No. 7,145,506, U.S. Pat. No. 7,386,150, and U.S. Pat. No. 7,265,709.
A non-ionizing radiation scanning device must scan a volume in space in order to generate an image. The time required to implement the scan is a function of the data acquisition rate and the size of the volume. Due to the large volume required to image, for example, a human, the refresh rate can be slow giving rise to movement-related blurring of the image.
The invention is directed towards achieving improved performance in operation of a scanning system.